Estudos funcionais de genes envolvidos na manutenção da estabilidade genômica : caracterização de gene hHC1 humano e da DNA polimerqase -PAK de Trypanosoma cruzi.

Abstract

The cells presents diverse systems able to protect the genetic material of the actual damages for ambient agents or products proceeding from the proper metabolism. The DNA repair system consists in sets of different proteins, which that, depending on the nature of their enzimatic activity, acts in diverse enzymatic pathways in order to correct most of generated injuries. Each time becomes more evident the importance of studies involving factors associates the systems that "protect" the genetic material, in order to prevent genetic illnesses or can result in the death of the organism. Ahead of this fact, the characterization of new involved genes in the process of maintenance of the genomic stability becomes necessary. In this work we describe the initial characterization of two genes, both involved ones in the maintenance of the genomic stability: the human hHC1 (human heterolougous complementation gene 1) and of the DNA polimerase -PAK of Trypanosoma cruzi. The hHC1 gene, isolated from a fetal human cDNA library, shown able to correct sensitivity fenotype caused by the genotoxic agent methyl-methane sulfonate (MMS), of one E.coli strain, deficient in base excison repair pathway. The nucleotide sequence of this clone disclosed the presence of three ORFs (open reading frame). Each one of the JALs was tested in survival curves and only the biggest, with 60 amino acids, exhibits the functional complementation activity in mutant E.coli strains. Moreover, this gene was able to complemente different strains deficient in different steps of nucleotide excision repair, in vivo and in vitro experiments, after the treatment with UV light. The DNA polymerase -PAK gene of Trypanosoma cruzi, the causative agent of Chagas disease, codifies an enzyme that presents polymerase activity with low capacity of distinction between its substracts, and seams to be a more permissive DNA polymerase. Probably it could acts as "an accessory" enzyme, that would resolves unusual structures in DNA, that would normally not be resolved by the DNA polymerase . Therefore, in this work, we initiate the characterization, by in vivo and in vitro assays, of two genes: one human and another from Trypanosoma cruzi, both involved in the maintenance of the stability of the genomes. The agreement on the processes of response and repair of the DNA is a basic matter to better understand the genetic variability in T. cruzi, as well as, for the study of possible drugs for the treatment of the Chagas disease. In addition , the study of human fetal genes could consists in a important tool for the elucidation of the embryonic development of this organism and, also, elucidation of possible illnesses associates with the activity of genes related of DNA metabolism.